Alkylation of isoparaffinic hydrocarbons



26, 1944; w, BRADLEY ETAL" 2,365,860

ALKYLATION OF ISbPARAFFINiC HYDROO ARBONS Filed June 18, 1941 -,1 Condem'er Reaction I Separator 1 Alylazed J9 rvcar'bom INVENTORJ mam 5. Bradley &' Jzarl J. Jzorpz' ATTO EY Patented Dec. 26, 1944 2,365,860 ICE ALKYLATION OF ISOPARAFFINIC HYDROCARBONS William E. Bradley, Los Angeles, and Karl J. Korpi, Redondo Beach, Calii'., assignors to Union Oil Company of California,

Los Angeles,

Calif., a corporation of California Application June 18, 1941, Serial No. 398,645 4 Claims. (01. 26(l683.4)

The present invention relates to the synthesis of hydrocarbons, and refers more particularly to the manufacture of paraflinic hydrocarbons of a branched chaintype suitable for use in automobile and aviation engines. he more specific sense the invention comprises a process for the combining of isoparaflinic hydrocarbons of relatively low molecular weights with olefinic hydrocarbons to produce branched chain parafilnic hydrocarbons of higher molecular weight and boiling within the gasoline range, which are of particular value as motor fuels or constituents thereof in that they possess unusual .anti-detonating characteristics. The invention further comprises the use of special catalysts and conditions of operation for the manufacture of these valuable compounds. This case is a continuation, in part, of our copending application, Serial No. 204,355, filed April 26, 1938.

The comparatively recent adoption of high compression ratios in automobile and aviation engines to increase their thermo-dynamic efficiency placed a demand upon the petroleum refining and similar industries to furnish hydrocarbon "motor fuels of a high anti-knock or slow burning character. Thus, in the aviation industry there is an'insistent demand for gasolines having'knock ratings of 100 octane (as determined by the A. S. T. M. method) and, containing not more than three milliliters of tetraethyl lead per gallon of gasoline.

In an attempt to provide motor fuels having the above characteristics and also satisfying other requirements, it has been recently proposed to produce synthetic fuels by combining aromatic or isoparafiinic hydrocarbons with olefinic hydrocarbons.' This reaction, realized in the liquid phase, involves the contacting of the above mentioned hydrocarbons in the presence of a suitable catalyst. To prevent polymerization, i. e. the combining of two or more olefinic molecules into a single molecule, and to permit the addition of the olefinic hydrocarbon molecule to the aromatic or isoparafiinic molecule, this liquid phase alkylation is preferably realized by first commingling the aromatic or isoparafiinic hydrocarbons with a catalyst, such as sulfuric acid, and then introducing the olefins or olefincontaining gas, the mixture being maintained in a state of agitation to provide adequate contact between the two hydrocarbon fractions to be interacted. The catalysts employed for this alkylation reaction include sulfuric. acid, aluminum chloride, etc.

The reaction between isoparaifinic hydrocarbons and olefins, to produce alkylated hydrocarbons or alkylates, may, however, also be realized in the vapor phase, this alkylation reaction possessing certain advantages peculiar to the va por phase treatment. Thus, the vapor phase alkylation of isoparaifins, of the type of isobutane and isopentane, with normally gaseous or normally liquid olefins does not require any subsequent fractional distillation of the products of reaction. This is because the vaporous or gaseous mixture leaving the reaction chamber may be conveyed into a condenser which is maintained at such a temperature that the alkylates are condensed without liquefying the unconverted hydrocarbons. As an example, the mixture of the isoparafiinic and olefinic hydrocarbons to be interacted may be conveyed as a gaseous or vapor mixture, and at optimum temperatures and pressures, through the reaction chamber containing a suitable alkylation catalyst described more fully hereinbelow. The products of reaction leaving this reaction chamber, aside from alkylated isoparaifins, also contain a certain proportion of unreacted hydrocarbons. This mixture may then be conveyed through the aforementioned condenser wherein the alkylates are caused to condense. These alkylates may then be easily removed, while the unreacted hydrocarbons, predominating in unreacted isoparaifins, may be recycled through the system after the addition of optimum or suitable quantities of the olefins.

Another advantage of the vapor phase process resides in the fact that it is possible to employ high temperatures without the necessity of operating at the vapor pressures of the hydrocarbon treated. These operations at the relatively high temperatures favor the rate of reaction, thus increasing the yield of alkylates per unit of time. A still further advantage resides in the fact that the treatment of the hydrocarbons in the vapor phase permits a control of the reaction, since it is possible to mix thoroughly the olefinic hydrocarbons with the isoparaflinic hydrocarbons to be alkylatedbefore introducing the mixture into the reaction chamber; This thorough commingling prevents any possible local over-concentration of the olefins, thus decreasing the tendency of these olefins to polymerize, and simultaneously favoring the desired alkylation reaction.

The term isoparaflins or isoparaffinic hydrocarbons," as employed in the present specification and claims, relates to the lower members of the paraflin series, namely to isobutane, isopentane and isohexane. It has been discovered, however, that the rates of alkylation of these isoparaflinic hydrocarbons, while maintaining other conditions equal, are not the same. Thus, the rate of alkylate formation wlien isopentane is employed is considerably lower than the rate of alkylation of isobutane, while the alkylation rate for isohexane is even still lower.

As to the terms olefins and "olefinic hydrocarbons, they are used herein to denote both the normally gaseous olefins and the normally liquid olefins, The normally gaseous olefinic hydrocarbons comprise the unsaturates between propylene and the pentenes, while the liquid olefins include the hexenes and other olefins of greater molecular weight. However, as will be brought outmore fully hereinbelow, it is preferable not to employ the very high boiling olefins since the conditions then become unfavorable for the alkylation of the specified isoparafiins. It is now peratures and pressures. Thus, even for the lowest molecular weight isoparaflinic hydrocarbons to be alkylated, as for example when isobutane is to be alkylated according to the present process, the temperature need not exceed about 750 F. These temperatures, depending on the hydrocarbons to be alkylated, may preferably be between about 100 and 600 F. Also, the pressures necessary are comparatively low, being preferably in the neighborhood of 20 to 300 pounds per square inch. Obviously, the optimum operating temperatures will vary with the pressures employed. For example, instead of operating at the above relatively low pressures, the reaction may be realized at considerably higher pressures, for example, up to 1000 pounds per square inch and even higher without in any way impairing, and even increasing, the reaction rates.

The alkylation reaction may be performed in the presence of any suitable catalyst, for example. sulfuric acid, mixtures thereof with phosphoric acid, or of these catalysts with other substances, such as certain metallic salts which tend to favor the alkylation reaction. When using a liquid catalyst, the mixture of hydrocarbon vapors or gases to be treated may be bubbled through the catalyst maintained at a suitable temperature. It has been discovered, however, that the use of solid catalysts is highly effective and results in high yields of alkylates without the formation of polymers and similar undesirable side reactions. It has been further discovered that metallic halide aluminates such as, for instance, the sodium, potassium or iron chloraluminates as such, or on a suitable support and in the presence or absence of a halogen acid are excellent catalysts for the alkylation in a vapor phase. Also solid acid sulphates and mixtures of these with acid phosphates, such as zinc or cadmium acid sulphates or phosphates alone or on suitable supports may be employed very effectively. Another group of catalysts which has been found to cause the alkylation of the isoparafflnic hydrocarbons, when realizing the reaction in the vapor phase, includes the solid catalysts formed by the partial saturation of activated carbon or bleaching clays and similar earths with sulfuric acid or mixtures of sulfuric and phosphoric acids, as .well as with these acids in combination with certain metallic activators which tend to favor the alkylation in preference to the polymerization of the olefins conveyed through the reaction zone. These metallic ac 'vators include the sulphates, phosphates, acetates, chlorides, nitrates and oxides of metals such as cadmium, zinc, copper, mercury, silver and barium. The use of the above described solid alkylation catalysts has been found to increase considerably the yield of alkyiates as well as the possible rate of throughput of the hydrocarbons to be treated.

The invention may therefore be stated to reside broadly in the vapor phase alkylation in the presence of an alkylating catalyst. The invention still further resides in the vapor phase alkylation of isoparaiilnic hydrocarbons of less than seven carbon atoms per molecule, with olefins having more than two carbon atoms and preferably less than thirteen carbon atoms.

The invention still further includes the catalytic alkylation of isoparamnic hydrocarbons of less than seven carbon atoms per molecule, in a gaseous or vapor state, said reaction being conducted at temperatures below about 750 F., and preferably in the neighborhood of to 600 F., depending on the hydrocarbons being alkylated. Still further, the invention includes the realization of the above vapor phase alkylation at pressures of between about 20 and 300 pounds per square inch.

More specifically, the invention may be stated to reside in reacting low molecular weight isoparaflinic hydrocarbons of the type of isobutane, isopentane, and isohexane, with oleflnic hydrocarbons above ethylene and below about dodecene, said reaction being realized in a vapor phase, in the presence of an alkylating catalyst, and at temperatures of below about 750 F. and pressures in the neighborhood of 20 to 300 pounds per square inch, whereby the products of reaction comprise branched chain hydrocarbons boiling within the gasoline boiling range, having high anti-detonating characteristics, and being substantially free from polymers within said gasoline boiling range. As previously stated, the above vapor phase reaction may be conducted at temperatures between about 100 F. and 600 F., depending on the hydrocarbons treated and on the pressures employed.

In a more specific sense the invention resides in the vapor phase treatment of the above isoparafllns with normally gaseous olefins above ethylene, in the presence of an alkylating catalyst and at optimum temperatures and pressures, to produce alkyiates boiling substantially within the gasoline range and being substantially free from polymers boiling within said range. The invention also includes the vapor phase treatment of isoparaflins below isoheptane with normally liquid olefinic hydrocarbons having less than thirteen carbon atoms per molecule, at temperatures of below 750 F. and pressures of between about 20 and 300 pounds per square inch, and in the presence of a suitable alkylating catalyst, to produce predominantly alkylates boiling within the gasoline range and substantially free from "products of polymerization within said range.

The invention also covers the treatment of the above isoparaflir'iic hydrocarbons with the defined olefins, in the vapor phase and in the presence of a solid catalyst, to produce *branched chain saturated hydrocarbons boiling within the gasoline range, having high anti-detonating characteristics, and being substantially free from olefin polymers boiling within said range. The invention still further includes the commingling of thevapors or gases of the above described isoparafllnic and oleflnic hydrocarbons,

and the bringing of said mixtures, at optimum temperatures and pressures, in contact with solid catalysts of the type of the metallic halide aluminates, such as the sodium, potassium and 2,885,860 iron chloraluminates, in the presence of a halokylated with the oleflns, in a vapor state,

through a reaction zone containing an alkylating catalyst maintained at a suitable temperature, continuously withdrawing the products of reaction from the reaction zone, and continuously cooling these products to a temperature at which the products of alkylation formed during the reaction are caused to condense without liquefaction of the unreacted or nonalkylated hydrocarbons. The invention further includes the separation of the alkylates from. the uncondensed' hydrocarbons, and the continuous recycling of the vaporous or gaseous hydrocarbons through the reaction zone, after the addition of and the commingling with suitable or necessary quantities of the olefinic hydrocarbons. In

this embodiment of the invention, additional quantities of the hydrocarbons to be alkylated may be continuously or periodically introduced into the system to make up for the hydrocarbons which have been used up in theformation Obviously, to conduct this va- I nor phase alkylation, 'these hydrocarbons must of the alkylates.

necessarily be in a vapor or gaseous state prior to the time when they come in contact with the alkylating catalyst. Also, the outlined continuous vapor phase alkylation may be realized at temperatures below about 750 F. (and preferably between about 100 F. and 600 F.) and at pressures in theneighborhood of between about 20 and 300 pounds per square inch or higher.

The term gasoline boiling range as employed herein refers to the average boiling range of fuels employed in ordinary automobile engines. Generallyspeaking such a gasoline has an initial boiling point of around 100 F., and a maximum or end point of about 425 F.

regulate the temperature within the reactor H). The mixture of' hydrocarbons to be reacted is introduced into reacting chamber I0 through line IS, the isoparafllnic hydrocarbons being fed into said line through branch l9 (provided with a valve The oleflns or olefin-containing gases are introduced into the system through line- 2| also equipped with a valve 22.

The products of reaction leave reactor I0, and are conveyed through line to a condenser 26 which is preferably maintained at a temperature' which will cause the fractional condensation of the alkylates produced without liquefying the isoparafllnic hydrocarbons being treated.

The liquid vapor mixture thus formed is then removed from condenser 26 and conveyed through line 21 to a separator 28 wherein the alkylates are caused to separate from the uncondensed fractions. These alkylated branched chain parafllnic hydrocarbons or alkylates may then beremoved continuously or otherwise through discharge-pipe 29 having a valve 3|]. The uncondensed hydrocarbons (which comprise or include the hydrocarbons to be alkylated) are withdrawn from the upper portion of separator 28, and conveyed, through pipe 32 and blower or vapor circulating pump 33, back into line l8 wherein-they are commingled with new quantitles of oleflns before reintroduction into the alkylating reactor 10.

In operation, an isoparafllnic hydrocarbon, such-as isobutane may be continuously or periodically introduced into the system through line IS. The olefinic hydrocarbons or gases conbe in a liquid state and may be vaporized and Reference is nowhad to the accompanying V drawing which shows diagrammatically one embodiment of the present invention. As will'be, described hereinbelow, the drawing discloses a continuous method of vapor phase alkylation of an isoparamnic hydrocarbon of the class described with an olefin to produce motor fuels having high anti-detonating characteristics and substantially free frompolymers. It is obvious, however, that the method described can be employed equally in connection with a discontinuous or batch system.

Referring now to the drawing, the numeral 10 indicates a reaction chamber which contains a suitable catalyst ll. As shown, this catalyst '65 may be held in place on a suitable support I 2 which may be in the nature of a perforated plate.

For the purpose of maintaining the catalyst at the desired temperature, reactor l0 may be provi'ded with a Jacket I3 which may be heated or cooled (as the case may be) by any suitable means, such as steam, water, etc., introduced through line I4 and withdrawn from jacket l3 through discharge line l5. It is clear'that any other means mav be emnlmmd m nn'ntrnl and taining the same, may be introduced through line 2|, the rate of introduction being regulated by valve 22. Both hydrocarbon fractions are preferably brought to the desired temperature prior to theircommingling in line l8. Obviously, however, either or both of these fractions may heated to the optimum or desired alkylating temperature after their comminglin'g in line I 8. This mixture is then conveyed, at a predetermined rate, through reactor Ill and in contact with the catalyst ll maintained therein. The products of reaction leaving through line 25 are continuously cooled in condenser 28 so that only the alkylates (alwlated isoparaflins) are liquefied. After separation in 28, the unconverted isoparaffins are then continuously recycled back into line I8 where they are again mixed with additional quantities of oleflns. Since at least part of the isoparaiiins are continuously alkylated and withdrawn as alkylates through line 29, additional quantities of the isoparafllns may be added either continuously or periodically through line H.

The temperatures and pressures maintained may be varied to suit individual cases. Thus, in

the case of alkylating isobutanes with oleflns inthe presence of a catalyst comprisin sulfuric acid absorbed on active carbon, the hydrocarbons may be heated to between about and F., and maybe conveyed at a pressure of 40 pounds per square inch through the reactor. Obviously, these pressures. etc., are only indicative, and are not to be considered as limiting,

lino-n vn rinuon...-

retically necessary to combine with the olefins..

For this purpose, the mixture of hydrocarbons being conveyed to reactor l should always contain an excess of isoparaffins. The isoparafilns remaining unaffected at the end of each cycle may then be recommingled with additional quantitles of the given olefins. As stated, additional quantities of the isoparafiins may also be introduced to take the place of the portion alkylated. In the continuous process described, it is possible to add the olefins continuously, while maintaining an excess of the isoparaflins in the system. The presence of this excess of isoparaffins and the relatively gradual addition of olefins prevents any local overconcentration of the olefins which would otherwise favor polymerization instead of the alkylation of the isoparaflinic hydrocarbons. In other words, the constant presence of an excess of isoparaflinic molecules in the gaseous or vapor mixture, increases the chances of an immediate or substantially immediate contact of an activated olefin with an activated isoparaflin molecule. Simultaneously, the relatively slow addition of the olefins decreases their concentration in the mixture, thus also increasing the possibilities of the alkylation reaction to take place in preference to the polymerization of these olefins.

Briefly stated, alkylation reaction between an isoparaflinic hydrocarbon and an olefin, in the presence of an alkylating catalyst may be of a simple character. Thus, an isobutane molecule may combine chemically with a butene to produce a branched chain paraflinic hydrocarbon which is an octane. In other words this straight alkylation is in the order of a simple addition of an introduced olefin molecule to an isoparaffinic molecule. -However, the reaction is somewhat more complex. Thus, when the specified isoparaifins are reacted'with the normally liquid olefinic hydrocarbons, the reaction product comprises a large proportion of saturated hydrocarbons of a branched chain structure boiling substantiallywithin the gasoline range. Such hydrocarbons evidently could be formed by an initial scission of at least one of the original reacting hydrocarbons into two or more hydrocarbons of lower molecular weight, and by the subsequent reaction between these lower molecular weight hydrocarbons to produce the alkylated branched chain saturated hydrocarbon molecules. In the alternative, the above phenomena may be the result of a simple addition of the introduced olefinic molecules to the isoparafiinic molecules, followed by a scission of the product. Specifically, this alkylation reaction may be termed cracking alkylation in order to distinguish it from the straight or simple addition of an introduced olefin to an isoparafiln, as this has been described hereinabove. Therefore, the "cracking alkylation reaction may be described as including the step of reacting of olefin molecules with isoparailin molecules to produce isoparafilnic alkylate molecules which have molecular weights of less than that obtainable if the reaction was of the simple addition type 'salt activator.

in which one olefinic molecule reacts with one isoparafllnic molecule to produce an alkylate molecule having a molecular weight equal to the sum of the molecular weights of the reactin olefin and isoparaflin molecules.

Therefore, the reaction between the isoparaffins of the class described and certain of the olefins, in the vapor phase and at the optimum temperatures and pressures outlined hereinabove, may result in both the simple alkylation of the isoparaffins by the olefins added, and in the cracking alkylation in which, as stated, alkylates are produced which have a lower molecular weight than would be obtained by the simple addition of an isoparafiin to an added olefin. The higher molecular weight olefins having molecular weights in the order of that of dodecenes and above, however, appear to be unsuitable to react with isoparaflins to form alkylates boiling within the gasoline range.

While the foregoing has been described in connection with an alkylation operation in the vapor phase, it will be observed that the alkylation process may be conducted under suitable temperature and pressure conditions in substantially the liquid phase. For example, relatively low temperatures of the order of to 200 F. and relatively high pressures of the order of 300 pounds per square inch to maintain the hydrocarbons in the liquid phase may be employed. This liquid phase reaction is'preferably carried out in the presence of the solid type catalyst herein mentioned such as the metallic halide aluminates, acid sulphates and acid phosphates.

It is to be understood that other modes of applying the principles of the present invention may be employed in lieu of those explained, all of these modifications and changes being deemed to be within the scope of the appended claims.

We claim:

1. A process for interacting isoparaflinic hydrocarbons having' less than seven carbon atomsper molecule with olefin hydrocarbons of more than two and less than thirteen carbon atoms per molecule to produce alkylated hydrocarbons boiling within the gasoline range which comprises commingling said isoparafilnic hydrocarbons with said olefinic hydrocarbons and conveying said mixture through a reaction zone containing a compound selected from the class consisting of solid acid sulphates and mixtures of said solid acid sulphates with acid phosphates.

2. A process for interacting isoparaflinic hydrocarbons having less than seven carbon atoms per molecule with olefin hydrocarbons of more than two and less than thirteen carbon atoms per molecule to produce alkylated hydrocarbons boiling within the gasoline range which comprises commingling a vapor of said isoparafflnic hydrocarbons with a vapor of said olefinic hydrocarbons and conveying said mixture through a reaction zone containing a compound selected from the class consisting of solid acid sulphates and mixtures of said solid acid sulphates with acid phosphates.

3. A process according to claim 1 in which the reaction is carried out in the presence of a metal 4. A process according to claim 1 in which the compound is zinc acid sulphate.

WILLIAM E. BRADLEY.

KARL J. KORPI. 

